Women who spend as little as 1 hour walking each week can cut their risk of heart disease in half.

The study found that walking, even at a moderate clip, reduced heart disease risk among nearly 40,000 women, including those who smoked, were overweight and had high cholesterol.

The study may come as good news to many women who loath to sweat but have nonetheless tried to jog, spin, kickbox and step-aerobicize their way to good health.

Current guidelines for physical activity recommend at least 30 minutes of moderate-intensity exercise such as brisk walking, on most days of the week. Previous guidelines recommended vigorous activity such as jogging or cycling, for at least 20 minutes three times a week to lower heart disease risk.

Previous recommendations for vigorous exercise are very daunting to women who are currently sedentary. The level of physical activity associated with benefit for heart health in our study is very modest and can be attained by almost everyone.

Heart disease is the leading cause of death among US women, and physical activity has been shown to lower the risk substantially. According to the Centers for Disease Control and Prevention, nearly one third of US women do not exercise at all during their leisure time.

The study found that women who walked for up to 1 hour over the course of a week lowered their heart disease risk by 14% compared with women who did not exercise. Those who walked 1 hour to 1.5 hours a week at a pace of at least 3 miles per hour reduced their heart disease risk by 51%.

Walking for at least 2 hours cut the risk only slightly more, probably because even a little exercise can have profound effects on those who are mostly sedentary.

The study clearly shows that women who engage in physical activity have lower rates of heart disease, and you don't have to be a triathlete.

In other findings, vigorous exercise was associated with a lower risk of heart disease than light exercise was. What's more, women who exercised the most had the lowest rates of high blood pressure, high cholesterol and diabetes.

They were also less likely to smoke, and consumed more fruit, vegetables and fiber than their sedentary peers did. In addition, they drank less alcohol and were more likely to use hormone replacement therapy, which is associated with a lower risk of heart disease.

The Journal of the American Medical Association March 21, 2001;285:1447-1454